diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2023-08-23 19:08:06 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-08-24 16:25:15 -0700 |
| commit | dce8f8ed1de1d9d6d27c5ccd202ce4ec163b100c (patch) | |
| tree | 93e6156402383138221d53cb0937d28cefa97cf0 /include/linux/sched/signal.h | |
| parent | ed1af26cd24811c3ddb5e7a276e3c6362c989bba (diff) | |
document while_each_thread(), change first_tid() to use for_each_thread()
Add the comment to explain that while_each_thread(g,t) is not rcu-safe
unless g is stable (e.g. current). Even if g is a group leader and thus
can't exit before t, t or another sub-thread can exec and remove g from
the thread_group list.
The only lockless user of while_each_thread() is first_tid() and it is
fine in that it can't loop forever, yet for_each_thread() looks better and
I am going to change while_each_thread/next_thread.
Link: https://lkml.kernel.org/r/20230823170806.GA11724@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'include/linux/sched/signal.h')
| -rw-r--r-- | include/linux/sched/signal.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 0deebe2ab07d..0014d3adaf84 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -648,6 +648,10 @@ extern void flush_itimer_signals(void); extern bool current_is_single_threaded(void); +/* + * Without tasklist/siglock it is only rcu-safe if g can't exit/exec, + * otherwise next_thread(t) will never reach g after list_del_rcu(g). + */ #define while_each_thread(g, t) \ while ((t = next_thread(t)) != g) |